1. Field of the Invention
The present invention relates to a light source unit which includes a wheel in which a luminescent material layer is provided in a circumferential direction and a projector which includes the light source unit.
2. Description of the Related Art
In these days, data projectors are used on many occasions as image projection apparatuses which project images of screens and video images of personal computers, as well as images of image data stored in memory cards on to a screen. These projectors are such that light emitted from a light source is caused to converge to a micromirror device called DMD (Digital Micromirror Device) or a liquid crystal plate for display of a color image on the screen.
In projectors of the type described above, conventionally, projectors using a high-intensity discharge lamp as a light source have been the mainstream of projectors. In recent years, however, there have been made many developments and proposals on light source units which utilize a semiconductor light emitting device such as a light emitting diode (LED), a laser diode (LD), or a device utilizing organic EL technology as a light emitting device of a light source unit.
Japanese Unexamined Patent Publication No. 2004-220015 (JP-A-2004-220015) proposes a light source unit which includes light emitting devices and in which the light emitting devices are disposed in a matrix configuration in order to increase the quantity of light. In the invention of the patent document, however, bright points of the light emitting devices are increased, and therefore, the convergence of light emitted from the respective bright points to a single point by an optical system arranged downstream of the light emitting devices becomes difficult, leading to a problem that the light utilization efficiency of light emitted from the respective light emitting diodes is reduced.
In addition, Japanese Unexamined Patent Publication No. 2004-341105 (JP-A-2004-341105) proposes a light source unit which includes an optical wheel in which luminescent materials are disposed in a circumferential direction and an ultraviolet light emitting diode. The light source unit proposed in this patent document is configured so that ultraviolet light is shone on to the optical wheel from a rear surface side thereof as excitation light and light emitted from a front surface side of the optical wheel is utilized as light source light.
A light source unit that is to be used in a projector is required to generate at least light of wavelength bands of red, green and blue, which are the three primary colors of light. In a configuration which utilizes an optical wheel like one shown in JP-A-2004-341105, the three primary colors of light can be generated by disposing a red luminescent material layer, a green luminescent material layer and a blue luminescent material layer are disposed end to end in a circumferential direction of the optical wheel.
However, in the light source unit which utilizes the optical wheel in the red luminescent material layer, the green luminescent material layer and the blue luminescent material layer are disposed end to end in the circumferential direction, there is a problem inherent therein that in the event of the luminescent material layers of the respective colors are disposed uniformly, there has existed a problem that a difference in luminance between light beams of red, green and blue wavelength bands is increased.
Then, there is proposed a light source unit in which at least a plurality of luminescent material layers are disposed end to end in a circumferential direction of an optical wheel, a blue laser emitter is used as an excitation light source, and an independent light emitting device is added further as a light emitting light source.
In the light source unit configured in the way described above, the difference in luminance between the light beams having different wavelength bands can be reduced. However, since the non-use area is caused on the optical wheel, an effective use of this area has been a problem to be solved.